This application relates to a scroll compressor wherein a back pressure pocket is provided with a fluid supply from a discharge pressure chamber.
Scroll compressors are becoming widely utilized in fluid compression applications. In a scroll compressor, a pair of scroll elements each have a base and a generally spiral wrap extending from their base. The wraps interfit to define compression chambers. One of the two scroll elements is caused to orbit relative to the other, and as this orbiting occurs, compression chambers define between the wraps decrease in volume and an entrapped fluid is compressed.
There are many challenges with a scroll compressor. One challenge is that the internal pressure in the compression chambers tends to force the two scroll members away from each other. To address this challenge, a bias force is applied to urge the two scroll members together.
Scroll compressors are formed with a thrust bearing that acts in opposition to the bias force. The bias force is known to be behind a non-orbiting scroll member in some scroll compressors, and behind the orbiting scroll member in other scroll compressors. In scroll compressors wherein the bias force is placed behind the non-orbiting scroll member, the thrust bearing is on a rear face of the base of the orbiting scroll member. In scroll compressors wherein the bias force is behind the rear face of the orbiting scroll member, the thrust bearing is positioned at radially outer locations on a forward face.
It is known to use a seal that receives a partially compressed fluid as part of the thrust bearing. Typically, a tap taps fluid at an intermediate compression point to a seal chamber.
There are deficiencies with this arrangement. In particular, there are losses due to the cyclic feeding and draining of this back pressure pocket across the tap hole, as the tap hole orbits relative to the pocket. The fluid can actually be bypassed from one compression pocket to the next, with resulting efficiency losses. In addition, the width of the seal chamber must be sufficiently wide so the tap will always be in communication throughout the orbiting cycle.